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investigate the effect of light intensity from a lamp projecting its rays onto some Elodea pondweed, - to test the rate of photosynthesis.

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Introduction

Biology Coursework Aim I am going to investigate the effect of light intensity from a lamp projecting its rays onto some Elodea pondweed, - to test the rate of photosynthesis. The rate of photosynthesis is expressed in the equation: Water + Carbon dioxide Glucose + Oxygen 6H20 + 6CO2 C6H12O6 + O2 Apparatus This experiment requires the following equipment: * Elodea pondweed * Sodium Hydrogen Carbonate NaHCO3 * Capillary tube attached to a syringe * A stopwatch * A clamp stand Method * First cut a piece of elodea pondweed about an inch long and put into a syringe * Then with a finger over the end of the syringe, pour the NaCHO3 solution into it, until the syringe is 3/4 full. * Then with finger still over the end, insert the plunger and press hard to release bubbles. * Attach syringe via tubing to the capillary tube. * Then after tapping the bubbles away, push solution down to the foot of the capillary tube by pushing down the plunger. * Next pull the plunger gently upward and watch the oxygen bubble rise. Pull until a relevant measuring point is found. * Attach plunger to a clamp stand and elevate in the air. ...read more.

Middle

This after time forces the level of oxygen in the capillary tube down. This is what gives us the results. Prediction I think that the further the lamp is placed from the syringe. The slower the rate of photosynthesis will be. This is because the further away the lamp is, the less concentrated energy is available on the rays hitting the syringe. I will test results from 10, 15, 20, 25 and 30cm away from the syringe. This should establish a trend in the results. The results will be lower as the distance increases because the light has to travel further through the air to reach the lamp, so the light intensity would be higher for the lamp at 10 cm than at 30cm. Preliminary testing We used preliminary testing to establish the distances and timings for our results. We decided to set the experiment up and set the lamp away at 5cm. Then wait for the bubble in the capillary tube to move and then start watch. We timed for 8 minutes and took results after every minute. Total distance moved in tube (cm) Distance moved in tube each minute (cm) 5 5 6 1 8 2 9 1 10.5 1.5 11.5 1 13 1.5 14 1 Here it shows steady results over the period. ...read more.

Conclusion

Evaluation My results were accurate to a certain point. They're maybe some human error because we may have started the stopwatch too early or too late after the oxygen bubble had moved. In addition, the results called out may have been rounded up and so results may be changed slightly. Overall, I thought I had good results and they gave me good opportunity to make a good graph. I had only one anomalous result, which was at 10cm away. It was that it had moved 1.6 cm, whereas the other results at that distance were 0.9, 1.0, and 1.3cm. You will see it on the graph. The results may have been biased because December is not really the time for growing elodea pondweed. In addition, the pondweed we used each time may have been of a different length or maybe a old piece from a previous experiment. This may of suede my results. I could have improved my results by using a dark box placed over the experiment to keep the light in. Also, by using the same length piece of pondweed and a different piece every time. Also maybe trying different distances away from the syringe like 5cm or 7.5cm and so on. I think that my results resembled my prediction and my preliminary testing. It showed that the further away the lamp is the slower the rate of photosynthesis will be. ...read more.

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